That's been in our Terms since Day 1, I believe. It's not there's anything wrong with soliciting donations for a worthy cause, just that if there's one group that deserves a rest from donation requests, it's P/CALS. We always leave enough information so someone can visit the site knowing what to expect.
It is probably true that we refer far more often to other sites than vice versa, for a variety of reasons.
Best,
Laurie